Autonomic Nervous System

Question 1

What are the divisions of the autonomic nervous system?

Answer 1

Sympathetic and parasympathetic

Question 2

What does the autonomic nervous system consist of?

Answer 2

MOTOR neurons that:

• innervate smooth muscle, cardiac muscle and glands
• make sure body has optimal support for activities
• SUBCONSCIOUSLY controlled

Question 3

Are axons in the ANS myelinated?

Answer 3

Pre-ganglionic neurons are lightly myelinated

Post-ganglionic neurons are not myelinated

Question 4

If a pre-ganglionic axon doesn’t synapse onto a post-ganglionic neuron, where does it synapse?

Answer 4

Adrenal medulla; this releases epinephrine and norepinephrine into the blood stream

Question 5

What is the origin and length of fibers and the location of ganglia in the parasympathetic nervous system?

Answer 5

Origin: craniosacral (brain and S2-4)

Length: long pre-ganglionic and short post-ganglionic

Location: visceral effector organs

Question 6

What is the origin and length of fibers, and location of ganglia of the sympathetic nervous system?

Answer 6

Origin: Thoracolumbar (T1-L2)

Length: short pre-ganglionic and long post-ganglionic

Location: close to spinal cord

Question 7

What is the role of the parasympathetic division and what happens when it is active?

Answer 7

Parasympathetic = rest and digest
–> promotes maintenance activities and conserves body energy

• lowered blood pressure, heart rate and respiratory rate
• gastrointestinal tract activity is high
• pupils constricted and lenses accommodated for close vision
• diuresis = waste elimination

Question 8

What is the location of ganglia and effector organs of the PSNS CN III?

Answer 8

CN III = oculomotor

Location of ganglia: posterior orbit

Effector organ: eye –> ciliary muscle and sphincter pupillae

Question 9

What is the location of ganglia and effector organs of the PSNS CN VII?

Answer 9

CN VII = facial nerves

Location of ganglia

1. Pterygopalatine –> pterygopalatine fossa
2. Submandibular –> inferiro to lingual nerve

Effector organs:

1. Nasal, palatine and lacrimal glands
2. Submandibular and sublingual salivary glands

Question 10

What is the location of ganglia and effector organs of the PSNS CN IX?

Answer 10

CN IX = glossopharyngeal

Location of ganglia: otic ganglion –> infratemporal fossa

Effector organs: parotid salivary galnds

Question 11

What is the location of ganglia and effector organs of the PSNS CN X?

Answer 11

CN X - Vagus

Location of ganglion: intramural ganglion –> in walls of target organs

Effector organs: most visceral organs (distal large intestine, urinary bladder, ureters, and reproductive organs)

Question 12

What is the role of the sympathetic nervous system and what does it do when active?

Answer 12

Sympathetic nervous = fight or flight
–> promotes adjustments during exercise or when threatened

• blood flow is shunted to skeletal muscles and heart
• increased heart and respiratory rate
• bronchioles dilate
• liver releases glucose
• pupils dilate

Question 13

Where do the SNS neurons come from in the spinal cord?

Answer 13

Sympathetic neurons produce spinal cord lateral horns and they are found in segments T1-L2

Question 14

Where do the pre-ganglionic fibers pass through?

Answer 14

Preganglionic gibers pass through white rami communicantes to enter the sympathetic trunk (paravertebral) ganglia

Question 15

How many sympathetic trunk ganglia are there?

Answer 15

23

• 3 cervical
• 11 thoracic
• 4 lumbar
• 4 sacral
• 1 coccygeal

Question 16

What are the three things that a pre-ganglionic fiber could do after entering the sympathetic trunk ganglion?

Answer 16

1. Synapse at the same level –> effects skin and blood vessels
2. Synapse at a higher or lower level –> could go to one or more different levels, this is important because the sympathetic ganglion are only found in the T1-L2 region of the spinal cord and we have to be able to innervate the rest of the body
3. Synapse in a distant collateral ganglion anterior to the vertebral column –> post-ganglionic neurons go to innervate the organs

Question 17

Where do fibers emerge from in the SNS pathway to the head and what do they innervate?

Answer 17

SNS pathway to the head –> T1-T4

Innervates: skin and blood vessels of head, dilator muscles of the iris, and inhibit nasal and salivary glands

Question 18

Where do fibers emerge from in the SNS pathway to the thorax and what do they innervate?

Answer 18

SNS pathway to thorax –> T1-T6

Innervates: heart (cardiac plexus) and lungs (pulmonary plexus), thyroid gland and skin

Question 19

Where do fibers emerge from in the SNS pathway to the abdomen and what plexuses do they contribute to?

Answer 19

SNS pathway to the abdomen –> T5-L2

• celiac ganglion
• superior mesenteric ganglia
• inferior mesenteric ganglia

Question 20

What does the celiac ganglion innervate?

Answer 20

Liver, gallbladder, stomach, spleen, pancrreas and proximal duodenum

Question 21

What does the superior mesenteric ganglia innervate?

Answer 21

Pancreas, distal duodenum, jejunum, ileum, ascending colon and transverse colon

Question 22

What does the inferior mesenteric ganglia innervate?

Answer 22

Descending colon, sigmoid colon and upper rectum

Question 23

In the SNS pathway to the head, where do the fibers synapse?

Answer 23

Emerging from T1-T4, synapsing in superior cervical ganglion

Question 24

In the SNS pathways to the thorax, where do the fibers synapse?

Answer 24

Emerging from T1-T6, synapse in the cervical trunk ganglia

Question 25

In the SNS pathway to abdomen, where do the pre-ganglionic fibers synapse?

Answer 25

Emerging from T5-L2, travelling through splanchinic nerves to synapse in prevertebral/collateral ganglia *recall that this is the third option of what can happen with nerve fibers in the SNS - synapsing into a mesh of ganglia

Question 26

In the SNS pathway to the pelvis, where do the fibers synapse and what do those nerves innervate?

Answer 26

Pathways synapse in the sympathetic trunk ganglia Sacral splanchnic nerves innervate genitalia and bladder

Question 27

Describe the SNS pathway to the adrenal medulla

Answer 27

1. pre-ganglionic fibers pass directly to adrenal medulla without synapsing in celiac ganglion 2. Upon stimulation, adrenal medullary cells secrete norepinephrine and epinephrine into the blood

Question 28

Which neurotransmitter is released in larger quantity by the adrenal medulla?

Answer 28

Epinephrine

Question 29

What do cholinergic fibers release and what types of neurons are cholinergic?

Answer 29

Cholinergic fibers release ACh --> acetylcholine - sympathetic pre-ganglionic - parasympathetic pre and post-ganglionic - somatic motor neurons

Question 30

What neurotransmitters do Adrenergic fibers release and what types of neurons are Adrenergic? Are there any exceptions to this?

Answer 30

Adrenergic fibers release epinephrine and norepinephrine - most sympathetic post-ganglionic * exceptions: sympathetic post-ganglionic fibers secerete ACh at sweat glands and some blood vessels of skeletal muscles

Question 31

What types of receptors bind ACh and are they inhibitory or excitatory responses?

Answer 31

1. Nicotinic --> excitatory/stimulatory | 2. Muscarinic --> excitatory or inhibitory because of G-protein coupling

Question 32

Where are nicotinic receptors found?

Answer 32

Motor end plates of skeletal muscle cells, all ganglionic neurons of SNS and PNS, and hormone producing cells of adrenal medulla

Question 33

Where are muscarinic receptors found?

Answer 33

Muscarinic is a type of cholinergic receptors meaning they release ACh Found on all effector cells stimulated by post-ganglionic cholinergic fibers

Question 34

What types of adrenergic receptors are there and are they inhibitory or excitatory?

Answer 34

1. Αlpha --> generally stimulatory | 2. Beta --> generally inhibitory (except for the heart)

Question 35

What effects do norepinephrine and epinephrine have on adrenergic receptors?

Answer 35

Norepinephrine works better on stimulating α receptors Epinephrine stimulates α and beta receptors equally

Question 36

What are the receptor subclasses of α adrenergic receptors?

Answer 36

A1 --> constricts blood vessels and visceral organ sphincters, dilates pupils A2 --> stops the release of NE from adrenergic terminals, inhibits insulin secretion by pancreas, and promotes blood clotting

Question 37

What are the receptor subtypes for beta adrenergic receptors?

Answer 37

B1 --> increases heart rate and strength B2--> (mostly inhibitory) dilates blood vessels and bronchioles, relaxes smooth muscle walls of digestive and urinary visceral organs, relaxes uterus B3 --> releases energy from fat cells

Question 38

What does dynamic antagonism mean in the context of the autonomic nervous system?

Answer 38

Parasympathetic and sympathetic systems working together for precise control of visceral activity --> they do opposite things hence "antagonistic"

Question 39

What does parasympathetic tone mean?

Answer 39

The PSNS normally dominates the heart and smooth muscle of digestive and urinary tract organs - works to slow the heart - dictates normal activity levels of digestive and urinary tracts - keeps blood vessels in a continual state of partial constriction BUT the SNS can override this in times of stress

Question 40

What are the four things that ONLY the SNS innervates and what control does the SNS therefore have?

Answer 40

1. Sweat glands and arrector pili --> SNS controls thermoregulatory responses 2. Kidneys --> SNS controls release of renin 3. Most blood vessels --> SNS controls blood pressure 4. Adrenal medulla --> SNS controls its metabolic effects; increased metabolic rates, blood glucose levels and the mobilization of fat for use as fuels

Question 41

What is the difference in the duration and localization of the effects in the SNS and PSNS?

Answer 41

PSNS: short-lived effects highly localized over effectors SNS: long-lasting, bodywide effects

Question 42

Why is sympathetic activation long lived?

Answer 42

NE is inactivated a lot slower than ACh NE and E released into the blood remain there until the liver can get rid of them

Question 43

What are the steps in the visceral reflex arc?

Answer 43

1. Sensory receptor in viscera 2. Visceral sensory neuron enters spinal cord dorsally 3. Integration center could be pre-ganglionic neuron, dorsal horn interneuron, or within walls of gastrointestinal tract 4. Efferent pathway to effector takes 2 neurons (pre and post ganglionic) 5. Visceral effector receives message and responds

Question 44

What is the difference between short and long visceral reflexes?

Answer 44

The short reflex happens in the organ and does not go to the CNS The long reflex goes all the way through the spinal cord or brain

Question 45

What are the four sympathetic visceral reflexes?

Answer 45

1. Cardioacceleratory reflex 2. Vasomotor reflex 3. Pupillary reflex 4. Ejaculation (in males)

Question 46

What role does the hypothalamus play in the ANS?

Answer 46

Overall integration

Question 47

What role does the brain stem play in the ANS?

Answer 47

Regulation of pupil size, respiration, heart, blood pressure, swallowing ect.

Question 48

What role does the spinal cord play in the ANS?

Answer 48

urination, deification, erection, and ejaculation reflexes